Discussion

To verify images, digital forensics investigators will often check whether the geometry of the scene is realistic. In a real photo, lines that run parallel in reality—like floor tiles—should meet at a single vanishing point. In this image, however, the dotted lines do not meet in a single point, indicating it is a fake. Image: an AI-generated image of soldiers marching down a hallway in three lines, wearing fatigues and carrying rifles. Four dotted white lines have been added over the image, running along the floor tiles visible in the foreground and extending back to where the vanishing point should be, behind the soldiers. Instead of meeting in a single point, the lines all cross at different points.

Investigators also examine reflections. The lines connecting points on an object to matching points in its mirror image run parallel in reality, so similarly should meet at a vanishing point. In this image, the lines again do not converge on one point, revealing it to be a fake. Image: An AI-generated image of a plastic cartoon dinosaur toy with its reflection visible in a small mirror. Four dotted white lines are layered over the image, connecting points on the toy with the same points on its reflection: the top of its eye, the end of its jaw, its hand, and its foot. The lines extend out to the side of the image, where they all cross at different points rather than meeting at a single point.

Shadows can be a giveaway, too. Because the Sun is so far away, its rays are essentially parallel when they reach Earth's surface. That means that the lines connecting points on an object to the shadows they cast in sunlight should also intersect at a vanishing point. In this Al-generated image, that is clearly not the case. Image: An AI-generated image of colorful, semi-transparent plastic cubes arranged in a group in a city plaza. Six dotted white lines are layered over the image, connecting corners of several cubes with the corresponding corners in their shadows. The lines extend upward off the edge of the image, toward where a vanishing point should be. Three of them converge on roughly the same point, but two extend further, and one cuts across all the others at an angle.